Intermittent overheating in my '01 cobra

4.6Stangrage

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first thing, I actually never let my '01 cobra overheat, it just gets hotter than it should. I first discovered it when I was on break at work the other day, I noticed it was running hotter than it normally runs which is slightly before the middle of the gauge. I didnt think to step out and look to see or hear if the fan was running or not. I can let it sit and idle for 45 minutes and it maintains normal temperature both of my attempts at diagnosis. When I was at a Drive thru, it was beginning to overheat until I got airflow to the radiator from driving it down the highway, that tells me that the thermostat is functioning as well as the radiator. the reservoir is full of coolant and I did a pressure test and found no leaks at all. Both upper and lower hoses have pressure and are hot when at normal operating temp. I was going to swap a fan relay if all possible but I cant do that because of the special cooling fan relay. I suspect this relay, has anyone had any issues these relays? have any other suggestions on a diagnostic path?
 

g36 monkey

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Are you sure the fan is coming on? The gauge is not supposed to be used for accuracy, it's mostly a dummy gauge so don't base your whole theory of "overheating" solely on the gauge, unless you have an aftermarket water temp gauge.
 

Wild Horses

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Do you have a handheld tuner? I've always known if my fan wasn't plugged in or not coming on after doing major work to the car and re flashing the tune. Fan should always kick on while reflashing. What's the weather like in your area now?
 

4.6Stangrage

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Do you have a handheld tuner? I've always known if my fan wasn't plugged in or not coming on after doing major work to the car and re flashing the tune. Fan should always kick on while reflashing. What's the weather like in your area now?

Yeah I have a BAMA tune, I tuned it over a month ago when it was 90 degrees out. Now its 75 during the day. Its odd because it happened at night so it was even colder out. Also I have not done any major work to it. I have just been driving it to work.
 

Wild Horses

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Yeah I have a BAMA tune, I tuned it over a month ago when it was 90 degrees out. Now its 75 during the day. Its odd because it happened at night so it was even colder out. Also I have not done any major work to it. I have just been driving it to work.

Then the easiest way to check the actual fan motor is plug your handheld in and reload the same tune file into the computer like normal. Just keep the window down and listen after you turn the key to "run" the last time the tuner prompts you to. If the fan kicks on (you will definitely hear your high speed fan if it's working) then it's good to go. Now if it doesn't turn on then it's most likely a simple relay, or ALOT OF TIMES A VERY BAD CONNECTION AT THE FAN plug ITSELF. Ford specifically still makes those replacement pig tails because it is still such a common issue from heat. Diagnosing fan temp trigger problems comes after this step.
 

4.6Stangrage

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Then the easiest way to check the actual fan motor is plug your handheld in and reload the same tune file into the computer like normal. Just keep the window down and listen after you turn the key to "run" the last time the tuner prompts you to. If the fan kicks on (you will definitely hear your high speed fan if it's working) then it's good to go. Now if it doesn't turn on then it's most likely a simple relay, or ALOT OF TIMES A VERY BAD CONNECTION AT THE FAN plug ITSELF. Ford specifically still makes those replacement pig tails because it is still such a common issue from heat. Diagnosing fan temp trigger problems comes after this step.

Yeah It started getting hot the other day at night time and the fan was on all the time. It never overheated, it just gets to about 3/4 of the way and maintains. Hmm, I would think my water pump is functioning but not as efficient as it should.
 

4.6Stangrage

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Then the easiest way to check the actual fan motor is plug your handheld in and reload the same tune file into the computer like normal. Just keep the window down and listen after you turn the key to "run" the last time the tuner prompts you to. If the fan kicks on (you will definitely hear your high speed fan if it's working) then it's good to go. Now if it doesn't turn on then it's most likely a simple relay, or ALOT OF TIMES A VERY BAD CONNECTION AT THE FAN plug ITSELF. Ford specifically still makes those replacement pig tails because it is still such a common issue from heat. Diagnosing fan temp trigger problems comes after this step.
Now that I am thinking of it, there could be a chance I put 87 octane in the cobra. I know it take at least 91 (which 93 isnt available in CA) but there could be a chance I filled the tank with it. I am definitely running 91 now so Ill see if it makes a difference.
 

Wild Horses

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Now that I am thinking of it, there could be a chance I put 87 octane in the cobra. I know it take at least 91 (which 93 isnt available in CA) but there could be a chance I filled the tank with it. I am definitely running 91 now so Ill see if it makes a difference.

If she's running the fan all the time and stays hot I would definitely throw a water pump in it and a new 170 thermostat since you're out in CA. Waterpumps on these are super simple. (Drain/remove/clean/replace/refill) I'd even say the thermostat takes more time than a water pump cause you gotta get under the car. Make sure that system is purged correctly also. My pump has been ready to croak for awhile now and since I'm replacing it anyway I'm gonna grab the SR Performance or Edelbrock. The impeller is designed like a turbo or Vortech compared to the factory one. But Autozone you'd prob spend $45 where as the upgrade is around 150. Keeping these big 4Vs cool with limited room for flowing air under the hood is key. Take it where you can get it.
 

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